Constructor exception doubt

[dolly shah]

public class Test20 extends A3{
    Test20()throws Exception{
        System.out.println("Test10 Class");
    }
    Test20(int i){}
    public static void main(String args[]) throws Exception{
        Test20 t = new Test20();
    }
}
class A3{
    A3() throws Exception{
        System.out.println("A Class");
    }
}

public class Test9 extends Base6{
   Test9()throws Exception{}
  Test9(int i) {}
   public static void main(String args[]) throws Exception {
      // try{
      //int i =0;
       new Test9();
       //}catch(Exception E){}
   }
}
class Base6{
   Base6() {
      System.out.println("Base");
   }
 

class A33 {
    A33(){}
 
         A33(int i) throws Exception {
                System.out.println ("Executing class A constructor");
          }
 

}
 
public class BB extends A33 {
          BB() {
                System.out.println ("Executing class B constructor");
           }
  BB(int i){
 }
           public static void main ( String args[] )  {
               new BB(32);
               new BB();
               
           }
}

Here I am posting 3 different codes. They all are related to super & sub class exception declaration.

As I conclude from all the code is, "If you are declaring an exception in no-argument super class constructor, you have to declare (not sure same) exception from the every constructor of the sub class."
Please correct me if I am wrong.

[nans nav]

Sub class Constructor by default calls the super class no-argument constructor. If no-argument constructor of super class is throwing an exception then it must be handled in sub class constructor.Thats the reason we need to add throws clause for no-argument constructor of sub class. But if Sub class Constructor explicitly calls the super class constructor with arguments which is not throwing the exception, then we dont need to handle the exception in subclass.

[dolly shah]

Any bartenders please can explain it?

[Burkhard Hassel]

Howdy cowboys,

just as nans (by the way, welcome to the Ranch
!! )

said.

This code compiles because the sub class does not call super() but super(int):

class Super {
Super () throws Exception {
}

Super(int i) {
}
}
 
class Sub extends Super {
Sub() {
super(17);
}
}

Remember that when you put in no constructor at all, a default constructor will be put in:

class BadSub extends Super {
}

will not compile, because behind the lines it calls the constructor of the two that does throw an exception:

class BadSub extends Super {
[I]// invisible default constructor:
BadSub() { // not declared to throw Exception
super();
}[/I]
}

Do you see know why BadSub does not compile?

Yours,
Bu.